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Teleclaw: Remote Robot Gripper 



Make] Projects 

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Teleclaw: Remote Robot Gripper 



Written By: Gordon McComb 



TOOLS: 



PARTS: 



Computer with internet connection (1) 

Drill and drill bits (1) 

plus a bit to start the cutout for the servo 

(optional) 

Multimeter (optional) (1) 
to test connections 

Picaxe USB programming cable, 

AXE027M) 

If you usea different Picaxe cable, you'll 

need a different connector than the 

3.5mm stereo jack specified above. 

Pliers: needlenose and lineman's 
(heavy-duty) (1) 

• Saw(s) (1) 

to cut the bracket; e.g. hacksaw, jigsaw, 
scroll saw 

Soldering iron and solder (1) 

Wire cutters (flush cutter type) and wire 
strippers (1) 



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MAKE Telerobotic Gripper Kit (1) 
item #MSTGK from the Maker Shed 
(makershed.com/teleclaw). includes all 
of the following project Materials 

Clamp, ratcheting plastic, about 5" long, 
with jaws that open at least VA" (1) 
such as Sears Craftsman #31594 

Servomotor, radio-controlled (R/C), 

standard size (roughly 

40mmx20mmx38mm), with double-arm 

horn(1) 

such as GWS S03N STD. Save your 

money and skip the fancy digital or 

metal gear servos. 

Picaxe 08M microcontroller (1) 

Infrared remote control (1) 
compatible with Sony equipment 

Infrared receiver/demodulator, 38kHz (1) 
Be sure it has a wide voltage range if 
using the Picaxe at less than 5V DC. 

• Gripper bracket (1) 
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Teleclaw: Remote Robot Gripper 



ready-made or cut from aircraft-grade 
plywood or expanded rigid PVC. 1 A " 
thick. 3 1 / 2 "x2" 

Stiff wire (1) 

unbent 2 1 /4 n coilless safety pin or a 3" 
length of 18 gauge or thicker steel or 
brass wire (not annealed) 

Solderless breadboard, half-size (1) 
Maker Shed #MKKN2 

Hookup wire, solid core (1) 
Maker Shed #MKEL1 

Stereo audio jack, 3.5mm (1) 

resistors (1) 

Capacitors, electrolytic, 15V or greater: 
4.7 F.47 F(1) 

LED.T1 3 / 4 (5mm) (1) 
any color 

Power supply, 5V DC, regulated, 200mA 

minimum (1) 

or battery holder with 3xAAA alkaline 

batteries (4.5V) or 4xAAA NiCd or NiMH 

rechargeable batteries (4.8V): for 

Picaxe. 

Power supply or wall adapter, 6V DC, 

750mA minimum (1) 

or battery holder with 4xAA batteries 

Machine screws, 4-40 pan head: V2" (4), 

3 /4"(2)(1) 

Nuts. 4-40 hex (6) (1) 



SUMMARY 

It might have been Robots of Saturn that first got my young brain thinking about building a 
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Teleclaw: Remote Robot Gripper 



mechanical man. In that obscure 1962 sci-fi adventure novel, Dig Allen and his fellow 
teenage space explorers transfer their thoughts into the bodies of teleoperated robots to 
mine Saturn's dangerous rings for precious Methane-X. 

Using some of my stepfather's "extra" ham radio gear, I tried to build my own telerobot, with 
plans of world domination swimming through my head. I didn't get far, but now, with powerful 
yet inexpensive microcontrollers, maybe this time it'll work. 

Big ideas begin with small steps, so let's start petite, cheap, and easy. Here's how to build a 
super-affordable remote robotic gripper that can pay the pizza delivery guy. 

The telerobotic gripper (let's call it the Teleclaw) has three main parts. The mechanics 
include a $2 plastic clamp, a radio-controlled (R/C) servomotor, some stiff wire, and a 
bracket to hold it all together. The electronics are a simple circuit designed around the 
Picaxe 08M microcontroller and an infrared (IR) receiver/demodulator module. 

The remote control unit is an ordinary TV/VCR/DVD remote. You can use a remote you 
already have or get a cheap one just for this project. I paid 99 cents for the model here, but 
note that cheaper remotes usually have shorter ranges. 

NOTE: Save time and money by picking up the MAKE Telerobotic Gripper Kit (item 
#MSTGK from the Maker Shed: http://www.makershed.com/teleclaw ), which includes 
all of the project materials. 



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Teleclaw: Remote Robot Gripper 



Step 1 — Construct the gripper mechanics. 




• If you're making your own gripper bracket, use rigid W plywood or expanded PVC, and 
follow the diagram. For a quick prototype you can use Vi" foam board. 

• Saw out the bracket's basic shape, then drill the mounting holes, all 1/8" unless otherwise 
noted. For the rectangular cutout (which will fit the servo), you can drill a starter hole and 
thread a thin saw blade through to cut out the rest, or else just cut through along the dotted 
lines shown in the diagram. 

• Secure the servo into the bracket using four 4-40x 1 /2" machine screws and nuts, with the 
shaft end near the bracket's bend. 



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Teleclaw: Remote Robot Gripper 



Step 2 




Drill hole here 
as needed 




• Drill 2 (or possibly 3) 1/8" holes through the clamp handles, one at the end of one grip (my 
clamp already had this) and 2 more 1" apart along the other, matching the 6" holes in the 
bracket 

• Use flush cutters to trim the plastic away from the clamp's handle around the red 
ratcheting piece, then yank out the ratcheting mechanism with heavy-duty pliers. 

• Mount the clamp to the bracket using two 4-40x 3 /4 n bolts and nuts. Make them tight without 
seriously deforming the plastic. 

Step 3 



• Drill a 1/8" hole toward the end of one side of a double-arm servo horn and temporarily fit 
the horn over the servo shaft. 

• Slowly rotate the servo counterclockwise until the motor hits its internal stop, then back off 
about 5°. 

• Reposition the horn so that its arms are in the 9 o'clock and 3 o'clock positions, then 
attach it to the servo using the included screw. 



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Teleclaw: Remote Robot Gripper 



Step 4 




,...^fl... Clip here 

and straighten 




♦ Clip off the clasp from a 2 1 /4 n coilless safety pin, straighten it, and cut a 3" length (or just 
start with 3" of stiff wire). Bend Vfc" of each end of the wire 90° in opposite directions to 
make a thin "S" hook 

• Hook the wire through the holes in the servo horn and the outside handle of the clamp. Use 
needlenose pliers to crimp the wire around the horn and handle loosely, so that it won't 
bind 



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Teleclaw: Remote Robot Gripper 



Step 5 — Build the gripper electronics. 




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To 

download I 
cable 




• Following the schematics, wire the circuit together on a solderless breadboard (you can 
transfer it to a soldered board later). Keep lead lengths short, especially for the 2 
capacitors. Leave one side of each battery pack unconnected for now. 

• For simplicity, this project uses 2 separate voltages, one non-regulated, to operate the 
Picaxe and the servo. See http://makeprojects.eom/v/27 for how to power the Teleclaw 
from a single 4.5V-5V supply. 

• Solder leads to the 3.5mm stereo jack, which the Picaxe programming cable will plug into. 
Connect the jack and 2 remaining resistors to your board as shown. All resistors must 
remain in place even after you've uploaded your program. 

Step 6 — Set up your remote. 

• If you're using a universal remote, follow its instructions for how to set it up for a Sony TV, 
VCR, or DVD player. With my remote, for example, I selected VCR code 098. The Picaxe 
08M has built-in commands for reading and decoding Sony SIRC protocol IR codes. 



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Teleclaw: Remote Robot Gripper 

Step 7 — Program the Picaxe. 

• Download and install the free Picaxe Program Editor (Windows) or AXEpad (Mac/Linux) 
software from http://www.picaxe.co.uk . Plug your programming cable between your 
computer's USB and the 3.5mm jack. 

• Launch the Program Editor or AXEpad, and specify "08M" under Options -» Target 
Device. Also select the serial port used with the download cable. 

• Download the project code here and open it in the editor. Apply power to the 
microcontroller circuit only — the servo doesn't need to be powered yet — and click the 
Program button to compile and transfer the code to your Picaxe. 



Step 8 — Now play! 




• Connect power to the servo, then 
disconnect and reconnect power to 
the Picaxe. The LED should glow to 
indicate when the Picaxe is 
sending pulses to the R/C servo, 
and the servo should quickly center 
itself. 

• Point the remote at the IR receiver 
on the breadboard and start 
pressing buttons to control the 
servo actions as follows: 

• Channel Up/Channel Down — 
close/open the gripper 
incrementally. 

• 2/8 — close/open the gripper 
fully. 

• 5 — set the gripper to midway. 

• — toggle the servomotor 
power on and off (to extend 
battery life). 



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Teleclaw: Remote Robot Gripper 



Step 9 




• The gripper should be closed, or 
nearly so, when the servo is 
rotated all the way clockwise. To 
adjust its range, unscrew the servo 
horn from the servo's motor shaft, 
reposition it, and put the screw 
back on. 

• The button toggles "active" mode. 
Press it once (the LED goes out), 
and the servo shuts off after each 
move, saving power and 
eliminating a slight jitter. Press 
again (the LED goes on), and the 
servo receives periodic pulses to 
set its position, which makes it 
maintain a tighter grip on things. 

• Comments in the code explain how 
to change parameters to fine-tune 
your Teleclaw. That's it! It's just 
that simple. In the next installment 
of Telerobots for World Domination, 
I'll tackle the job of creating a 
weapons system consisting of a 
pulsed atomic-powered rail gun and 
chemical laser. Stay tuned, fellow 
space explorers! 



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Teleclaw: Remote Robot Gripper 

Step 10 — Run the Telegrip from just one power source. 

• Radio-control servo motors can suck up a lot of current when they move. The telegrip 
avoids the many pitfalls associated with this problem by using a separate battery pack for 
the servo. 

• Depending on the torque rating and current draw of the specific model of servo you use, 
and the current capacity of your power supply, you might get by using just one power 
source. Unless you add voltage regulation for the PICAXE, you must run both circuit and 
servo from a power source of no more than 5 volts. Options include: 

• Set of three AA- or C-size non-rechargeable batteries (nominal 4.5 volts) in a battery 
holder 

• Set of four AA- or C-size rechargeable batteries (nominal 4.8 volts) in a battery holder 

• Regulated 5VDC power supply with 1 amp (minimum) output (most plug-in wall 
transformers are not regulated, so be sure to check) 

• You'll know you have problems when the servo draws too much current, causing the 
voltage to the PICAXE to sag below its brownout level. When this happens the chip will 
reset, or may function erratically. 

This project first appeared in MAKE Volume 27 . page 62. 

This document was last generated on 201 2-11 -01 11 :1 5:59 AM. 



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